Vacuum at EOSS

Mike Manes purchased a vacuum chamber so that various barometrically operated devices could be calibrated.

The chamber is made of Plexiglas with some structural reinforcement by means of those rods you can see surrounding the cage.

Below the chamber is the pump.

"Resting" pressure in millibars. We are the mile high city.

Mike removes the lid to place a test object in the chamber

Mike places a baro switch in the chamber

After pumping for a minute (more or less) the chamber is at 2 Torr or around 131,000 ft. ASL

Almost immediately upon evacuation startup the top, which is resting some gasketing material, bows inward towards the center of the chamber. When you have the chamber right before your eyes, this effect is quite pronounced. However, this particular angle doesn't show it off that well. You can make out the elevated corners pointing up while the center of the side edges of the plexiglas top are being sucked down close to the top surface of the chamber.

After running up to a very low pressure altitude, Mike allows the chamber to "descend" to 99 Torr (around 45,000 ft. ASL) where the baro switch is just barely being activated.

Returning to mile high Denver's pressure level, you can see the external air pressure has significantly collapsed the baro switch. It is now definitely "open".